Law enforcement officials from multiple agencies announced on Monday that 38 "notorious" gang members have been arrested as a result of investigations dating back to the summer of 2015 in an area of Los Angeles known as the Vermont Corridor.

The four-square-mile area along Vermont Avenue stretches from Hollywood Boulevard to 120th Street. The so-called Vermont Corridor Task Force is comprised of investigators from the Los Angeles Police Department, U.S. Marshals Service, Los Angeles County Sheriff's Department and the District Attorney's Office's Major Narcotics and Hardcore Gang divisions.

The group began investigating in response to an increase in gang violence that began in the area in early 2015, authorities said. The crimes included nine murders, as well as attempted murders and sexual assaults.

According to the officials, two of three gangs in the area forged an alliance to eliminate the third gang. Investigators believe the task force prevented three murders and the illegal transport of several hundred pills to Cleveland.

"I would say it's a severe blow to the gangs," Sheriff Jim McDonnell told reporters at a news conference at the Hall of Justice.

Deputy Chief Bill Scott, a 27-year LAPD veteran, described the investigation as "one of the smoothest operations that I've ever been involved in."

"That goes to the sheriff's (department) and their willingness to reach out to us and work with us on problems that we both have in common," Scott said.

McDonnell said fighting crime now includes trolling online activity as threats happen in real time, and there is an ability to get people together quickly. Therefore, the task force was expected to remain in place.

All of the 38 arrestees were men and 29 have been prosecuted, authorities said.